Conventionally, a fiber optical light guide using an optical fiber technology is used for an illumination for a vehicle, a building such as a house, or the like. For example, Patent Document 1 (JP H11-006918 A) describes such a fiber optical light guide. An example of a conventional fiber optical light guide is shown as a fiber optical light guide 1 in FIG. 12. As shown in FIG. 12, the fiber optical light guide 1 has a tubular clad member 2 and a core member 3 around which the tubular clad member 2 is positioned. The fiber optical light guide 1 has an elongated shape and a circular cross section. A light emitted from a light source such as a light-emitting diode (LED) 4 enters into the core member 3 from an inlet side as an incident light, and the light is transmitted toward an outlet side. Since a portion of the incident light is diffused from the clad 2 while being transmitted to the outlet side, the fiber optical light guide 1 entirely illuminates softly.
However, according to studies conducted by the inventor of the present disclosure, since the fiber optical light guide 1 illuminates entirely, the fiber optical light guide 1 works insufficiently to produce an illumination pattern, for example, showing a light going straight in one direction or a smooth gradation with various colors of lights. In this case, various illumination patterns may be produced by using multiple light guides 1 and multiple LEDs 4 that are positioned such that each LED 4 faces the corresponding fiber optical light guides 1, and by controlling a lighting pattern of the fiber optical light guides 1. However, it may require a lot of the fiber optical light guides 1 increases, which leads to an increase in the cost for the multiple light guides 1.